JPH01119902A - Sound recording and reproducing circuit - Google Patents

Abstract

PURPOSE:To eliminate the distortion of a signal at the time of sound recording and to reduce the number of the change over switch circuits for sound recording and reproducing by providing a second transistor between the collector of a first transistor in a reproduction amplifier circuit and one of power sources. CONSTITUTION:One of heads 1 for sound recording and reproducing and a sound recording signal transmission system are connected to the base 22 of the first transistor 22 in a reproduction signal amplifier 2, and the second transistor 52 is provided between the collector of the first transistor 22 and one of the power sources. Consequently, the circuits of the transistors 22 and 52 become equal to diodes 61-64 at the time of sound recording, and the diode 64 becomes the bias of an opposite direction, whereby it is impervious to be conducted. Even if >=0.6V of the sound recording signal is added to negative, distortion does not occur and the number of the circuits of the changeover switches S3 for sound recording and reproducing can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a recording/reproducing circuit used in a recording/reproducing apparatus such as a tape recorder.

Conventional technology Recording and playback circuits of recording and playback devices have traditionally been switched between recording and playback using mechanical switches, but recently there has been a trend toward switching over using electronic switches.

An example of the conventional recording/reproducing circuit mentioned above will be described below with reference to the drawings. FIG. 10 shows an example of a conventional recording/reproducing circuit. In FIG. 10, 1 is a recording/playback head, 2 is a playback signal amplification circuit, 3 is a recording bias signal generation circuit, 8 is a low frequency amplification circuit, 9 is a speaker, 10
is a recording signal amplification circuit, and Sly S2+ 83 is a changeover switch.

To explain the operation shown in FIG. 10, during the reproduction operation, the switch SIT S218s is connected to the A side, and the signal reproduced from the magnetic tape by the recording and reproduction head 1 is applied to the reproduction signal amplification circuit 2 through the switch Sl.
The signal is amplified through the transistors 22, 23, 24, 25, 26, 41, the capacitor 7, the low frequency circuit 8, and the speaker 9 produces a reproduced sound.

Next, during recording operation, switch SL+ S2e S3 is B
connected to the side. A signal for recording is applied to the terminal 11, amplified by the recording signal amplification circuit 10, and then connected to the resistor 5. A bias signal is applied to the recording and reproducing head 1 via the capacitor 6, and a bias signal is also applied from the recording bias signal generating circuit 3 to the recording and reproducing head 1 to be recorded on the magnetic tape.

Problems to be Solved by the Invention However, the above configuration requires a large number of switching circuits that use mechanical switches to switch between recording and reproducing operations.

In view of the above-mentioned problems, the present invention provides a recording and reproducing circuit that reduces the number of switching circuits between recording and reproducing operations.

Means for Solving the Problems In order to solve the above problems, the recording and reproducing circuit of the present invention connects one of the recording and reproducing heads and the recording signal transmission system to the base of the first transistor in the reproduced signal amplification circuit. However, a second transistor is provided between the collector of this first transistor and one power supply, and the base of this first transistor is biased to one of the power supplies at least during playback operation, and the playback signal is amplified in the playback state. The circuit is operated and the second transistor is turned on to amplify the playback signal, and in the recording state, the playback signal amplification circuit is made inactive and the second transistor is turned off. It is.

Effect of the present invention With the above-described configuration, even if the recording signal transmission system is connected to the recording/reproducing head and the base of the first transistor in the reproduced signal amplification circuit, the signal is not distorted during the recording operation by providing the second transistor. Moreover, the number of changeover switch circuits can be reduced.

Embodiment Hereinafter, a recording and reproducing circuit according to an embodiment of the present invention will be explained with reference to the drawings. FIG. 1 shows an electrical connection diagram of a recording/reproducing circuit in a first embodiment of the present invention. In FIG. 1, 1 is a recording/playback head, 2 is a playback signal amplification circuit, 3 is a recording bias signal generation circuit, 4, 6 .
7 is a capacitor, 8 is a low frequency amplifier circuit, 9 is a speaker,
10 is a recording signal amplifier, S3 is a changeover switch, 14゜2
2.23.24, 25.26.27.30, 35°36
．． 40.41.52, 56, 57 are transistors, 38
is a diode, 5.13.21., 28°51.29.
31, 33, 34, 37.39 are resistances.

The operation of the recording and reproducing circuit configured as described above will be explained below using FIGS. 1 to 9.

First, FIG. 1 shows an embodiment of the present invention,
During the reproducing operation, the switch S3 is connected to the A side.

The signal recorded on the magnetic tape is reproduced by the recording/reproducing head 1 and applied to the base of the transistor 22.
The sound is amplified by the transistors 23, 24, 25, 26, 41, passed through the capacitor 7 and the low frequency amplification circuit 8, and then reproduced sound is produced by the speaker 9. Next, during a recording operation, when a signal for recording is applied to the terminal 11, the recording signal amplification circuit 10. A bias signal is applied to the recording/reproducing head 1 via a resistor 5 and a capacitor 6, and a bias signal is also applied to the recording/reproducing head 1 from a recording bias signal generating circuit 3 to record on the magnetic tape.

If the transistor 52 is not present in this recording state, the collector of the transistor 22 is directly grounded, and the playback signal amplification circuit 2 is not supplied with voltage because the switch S3 is set to Ill. no current is flowing through it. For this purpose, the fifth
The part shown in the figure is almost equivalent to connecting diodes 61 and 62 as shown in FIG. Therefore, when the signal from the resistor 5 and capacitor 6 is applied to the base of the transistor 22, if the amplitude of the signal is swung to the negative side, the diode 62 becomes conductive at about 0.6 V, and the signal is clipped, as shown in FIG. become that way.

For this purpose, the embodiment of the present invention shown in FIG. 1 is provided with a transistor 22, and the circuit of the transistor 22, 52 shown in FIG.
．． 64, the diode 64 becomes reverse biased and no longer conducts, and even if the recording signal is applied negative by about 0.6 V or more, it will not be distorted. Moreover, the number of circuits for recording/playback changeover switches can be reduced.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is an electrical wiring diagram showing a recording/reproducing circuit according to a second embodiment of the present invention. In Figure 2, a differential amplifier is constructed using transistors 22 and 42 instead of transistors 23 and 24 that constitute the differential amplifier in Figure 1, and as in Figure 1, the collector of transistor 22 and the ground are connected. In between, a transistor 52 is inserted with its collector and emitter connected, and the transistor 52 operates so as to be on during playback operation and off during recording operation,
This has the same effect as in FIG.

Next, in FIGS. 3 and 4, a transistor 53 is provided to prevent the input resistor 21 in FIGS. 1 and 2 from lowering the impedance during recording operation, and the transistor 53 is turned on during playback. However, it is turned off during recording, making it possible to increase the impedance during recording. Since the transistor 14 is on during the recording operation, the base of the transistor 22 is grounded via the recording/reproducing head 1 and the transistor 14.

Other operations and effects are the same as in FIGS. 1 and 2.

As described above, by providing the second transistor between the collector of the first transistor of the playback amplifier circuit and one of the power supplies, signal distortion during recording can be avoided (and the number of switch circuits for recording and playback can be reduced). can do.

Effects of the Invention As described above, the present invention connects one side of the recording/playback head and the recording signal transmission system to the base of the first transistor of the reproduction signal amplifier, and connects the collector of the first transistor with one power source. A second transistor is provided in between, and the base of the first transistor is biased to one side of the power supply at least during the regeneration operation, and in the regeneration state, the reproduction signal amplification circuit is operated and the second transistor is turned on. to amplify the playback signal, disable the playback signal amplification circuit in the recording state, and turn off the second transistor to eliminate signal distortion during recording and reduce the number of recording/playback changeover switch circuits. be able to.

[Brief explanation of the drawing]

FIG. 1 is an electrical wiring diagram of the recording/playback circuit in the first embodiment of the present invention, FIG. 2 is an electrical wiring diagram of the recording/playback circuit in the second embodiment of the invention, and FIGS. The figure shows the third aspect of the present invention. 5, 6, 7, 8, and 9 are explanatory diagrams of the embodiment of the present invention, and FIG. 10 is an electrical wiring diagram of the recording/playback circuit in the fourth embodiment. FIG. 2 is an electrical wiring diagram of a recording/playback circuit. 1... Head for recording and playback, 2... Playback signal amplification circuit, 3... Recording bias signal generation circuit, 4°β, 7... Capacitor, 8...
・Low frequency amplifier circuit, 9...Speaker, 10...
... Recording signal amplification circuit, S I, S 2 + S
3...Choice switch, 14, 22, 23゜2
4.25.26.27,30,35.36.40゜41
．． 52.50.57...Transistor, 38.
...Diode, 5.13.21, 28.51°29.31, 33, 34.37.39...Resistance. , Name of agent Patent attorney Toshio Nakao and one other person Figure 5
Figure 6 Figure 7 Figure 8A Figure 9

Claims (1)

[Claims] One of the recording and reproducing heads and the recording signal transmission system are connected to the base of the first transistor of the reproduction signal amplification circuit, and a second transistor is provided between the collector of the first transistor and one of the power supplies. , the base of this first transistor is biased to one of the power supplies at least during the playback operation, and in the playback state, the playback signal amplification circuit is operated and the second transistor is turned on to amplify the playback signal and perform recording. 1. A recording/reproducing circuit characterized in that in this state, a reproduction signal amplification circuit is rendered inoperative and the second transistor is turned off.